This invention relates to a lubricative coating and filler material for restoring metal surfaces that have been scratched, scored, grooved or otherwise damaged to a functional condition to avoid costly repair procedures and minimizing scrap for metal components and methods for restoring a damaged surface of a substrate to a functional condition through application of a filler material consisting of an epoxy and tungsten disulfide.
In the past, when surfaces on metal components were damaged, it was common practice to repair scratches in worn areas by welding or brazing, then machining to restore surfaces to a functional condition.
Even though this type of repair was time consuming and expensive, it was more cost effective than scrapping the metal component. In an attempt to reduce cost, it was suggested that such damaged areas may be repairable through the use of a high performance epoxy material. However, it was not until molybdenum disulfide was added to the epoxy, as disclosed by the method and material in U.S. Pat. No. 3,950,571, that damaged surfaces could be restored practically and economically and especially those metal components that may be exposed to aviation fuel at temperatures above 350 degrees F.
While the molybdenum disulfide modified epoxy repairs are satisfactory for most applications it has been observed that voids may be present in the material applied to repair the damaged surfaces. In order to achieve a smooth and void free surface through the use of molybdenum disulfide modified epoxy, two or three applications are required in order to obtain a nonporous surface and machining is required after each application. Investigation revealed that a major cause of the voids and the resulting porosity in a repaired surface was the evaporation during the curing process of solvents used as a carrier for the modified epoxy mixture. The development of voids and a porous surface should be avoided or minimized in order to achieve maximum structural integrity better wear resistance and to minimize potential leakage problems through the repaired surface.
Upon reviewing the current problems, it was determined that a repair material should exhibit or possess the following properties or characteristics: a low coefficient of friction; minimum porosity; and good resistance to aviation fuel at temperatures above 350 degrees F. Further, when used to repair surfaces such materials should be nonporous, lubricate a surface and provide a machinable coating in a single application to reduce the time involved in making or restoring a surface to a functional condition.
One solution to these problems is to use a filler material consisting of a mixture of tungsten disulfide and a single part epoxy such as Hysol 929NA sold by Dexter Hysol Corporation as disclosed in U.S. Pat. No. 5,316,790. Another solution is to use a filler material consisting of a mixture of tungsten disulfide and a bismalemide such as Hysol EA9369 sold by Dexter Hysol Corporation as disclosed in U.S. Pat. No. 5,516,548. Both of these patents are assigned by the assignee of this patent application and are hereby incorporated by reference.
A disadvantage to these solutions is that Hysol 929NA and Hysol EA9369 are single component, heat activated systems that are thermally unstable during shipment. Because of this thermal instability, special storage and shipping conditions are needed to keep the components at or below 32xc2x0 F. so as to prevent uncontrollable exothermic reactions.
Accordingly, there is a need for a filler material consisting of a mixture of tungsten disulfide and an epoxy that overcomes the disadvantages of the prior art systems.
An object of the present invention is to provide a filler material consisting of a mixture of tungsten disulfide and an epoxy that is not exothermic under shipping conditions and therefore is easy to transport and handle.
Another object of the present invention is to provide a method of restoring a damaged and/or worn surface on a metal substrate to a functional condition.
The present invention meets these objectives by providing a method of restoring a damaged surface of a substrate to a functional condition through a filler material consisting essentially of tungsten disulfide epoxy resin having a 10:1 ratio of epoxy to tungsten disulfide. After the filler material is applied to the damaged surface it can be cured at room temperature, and/or heat cured by uniformly raising the temperature to a cure temperature of the epoxy to allow any volatiles to evaporate without the creation of voids in the surface such that the resulting porosity prevents corrosion of the substrate when exposed to aromatic fuels at temperatures of 350 degrees F. The filler material consists of tungsten disulfide and a two part epoxy such as Hysol EA 9394/C-2.
These and other objects, features and advantages of the present invention are specifically set forth in or will become apparent from the following detailed description of a preferred embodiment of the invention when read in conjunction with the accompanying drawings.